1. Field of the Invention
The present invention relates to an adapter of the type used for interconnecting two optical fibers, for example in the situation where it is required to connect a testing device, having an internal fiber, to an external fiber, for testing the external fiber or an optical circuit to which it is connected.
2. Prior Art
There is a common need to provide temporary connections between an internal optical fiber or fibers, which are part of testing equipment, and external fibers which are to be themselves tested or which are parts of optical circuits to be tested. The testing equipment is usually contained in a case having a panel providing terminals or xe2x80x9cadaptersxe2x80x9d which are connected internally to a testing device, usually incorporating a laser light source and/or a receiver, and which are capable of receiving connectors mounted on the ends of the external fibers. Sometimes the testing devices are permanently connected or xe2x80x9chard wiredxe2x80x9d to the internal portions of the terminals. More commonly however, the internal fibers have plug type connectors and the terminals are in the form of adapters which have a double ended receptacle with an inner part accessible from inside the panel for receiving the internal fiber connector, and an outer part on the outside of the panel for receiving a plug type connector at the end of an external fiber.
It is common for the adapters to have an alignment sleeve which is a close fit on ferrules fixed to the ends of each of the connected optical fibers. Apart from this, however, the connectors vary widely. Commonly used connectors are so-called FC connectors, having a nut which engages an externally screw threaded barrel portion of the adapter which surrounds the alignment sleeve, and ST connectors having a bayonet type connection to a similarly located barrel. Still others, known as SC connectors, have a rectangular plug which is a push fit into a rectangular socket and which is retained by latches. One known testing apparatus usually has internal fibers with FC type connectors. However, the apparatus may need to be used with external fibers having different types of connectors, and it would clearly be advantageous to have adapters capable of being changed to suit such different connectors.
Most adapters are designed to receive, in their opposite ends, two connectors of similar type, but some are known which can receive different types of connector. For example, U.S. Pat. No. 5,073,042, which issued Dec. 17, 1991 to Mulholland et al., shows a hybrid adapter comprising two parts, one designed to receive an FC connector, and the other to receive an SC connector, the two parts being joined by bolts. Clearly, different arrangements can be made by mixing and matching different end parts. However making such connections with bolts or the like is not practical for most users.
U.S. Pat. No. 5,297,227, which issued Mar. 22, 1994 to Brown et al., also shows an adapter formed in two parts, i.e. an inner part and an outer part, connected by the push fit of a cylindrical protrusion into a cylindrical housing. Each part can be one suited to any particular type of connector, so that different parts can be combined in different combinations depending on the types of connectors with which the optical fibers to be tested are equipped. A series of the internal parts is held by an instrument panel, and a series of the external parts is held by a mounting panel, the parts being held together by fixing the mounting panel to the instrument panel. Apart from this the adapters themselves do not have any means for holding the parts together.
U.S. Pat. No. 5,333,222, which issued Jul. 26, 1994 to Belenkiy et al., shows an adapter formed of two parts which are held together by latch arms, but it seems that this is a permanent connection and it is not intended that the parts be separated and used with different parts.
A different approach is used by Diamond S. A., for example as described in U.S. Pat. No. 5,444,806, which issued Aug. 22, 1995 to de Marchi et al. Here the panel carries a plug type connector with a protruding ferrule, which mates with a sleeve adapter which is movable and which has its outer end mated with another plug type connector. This has the drawback that the interior plug type connector is xe2x80x9chard-wiredxe2x80x9d to the device inside the testing instrument, rather than being connected by a removable connector as is usual, and when a device has to be added to the testing equipment, or changed, its end connector usually has to be removed and the end of its fiber spliced to a connector on the panel.
Another problem with the commonly used adapter arrangements, i.e. those in which the adapter is fixed to the panel, is the difficulty of cleaning the ferrule at the end of the internal fiber; dirty ferrules cause a large proportion of malfunctions in apparatus of this kind. While the external fiber ferrule projects from the end of the connector and is easily cleaned, the internal fiber ferrule can usually only be cleaned by opening the testing equipment case and removing the internal fiber connector from the adapter. Sometimes this is facilitated by making the panel removable, but this requires tools for removing the panel. In any event, there is a possibility of damaging the fiber by bending it too sharply, or harming other delicate devices in the case. It would be desirable to make the end of the internal fiber ferrule accessible from outside the case, for cleaning purposes.
It is one object of the invention to provide an adapter having two parts which are readily separable, i.e. do not require removal of screws or the like, so that the outer part can easily be adapted to the type of connector to be used. It is a secondary object to provide an arrangement in which removal of the outer part enables the internal fiber ferrule to be cleaned.
It is also desirable that the internal fiber ferrule be protected from contamination, and that users"" eyes be protected from laser light emitted from the internal fiber, when there is no connector present. Some prior art designs deal with the contamination problem by providing protective caps or dust covers which are a push fit onto the end of the adapter; however such devices are easily lost, and are not effective in protecting a user""s eyes. In other designs, a hinged shield has been used, which both prevents contamination, and also protects an operator""s eyes. Such a shield is shown in U.S. Pat. No. 5,506,922, which issued Apr. 9, 1996 to Grois et al., in the form of a flap mounted on the flat side of a rectangular SC type receptacle. This design would not be suitable for use with other types of adapter receptacle, most of which have a protruding barrel portion which receives an outer sleeve and so could not accommodate the kind of flap shown in Grois et al.
It is thus a further object of the invention to provide a shield or dust cover, both for limiting contamination, and for protecting a user""s eyes, and which is suitable for adapters designed for use with any commonly used connector type.
In accordance with one aspect of the invention, there is provided an adapter for interconnecting optical fibers connectors, having a first part for connection to a first optical fiber having an end ferrule, and a second part suitable for receiving optical fiber connector having a second optical fiber with a second end ferrule, the end ferrules being received in an alignment sleeve held within the adapter when both connectors are in place in the adapter,
wherein the second part is readily separable from the first part, the parts having complementary engaging surfaces, and having cooperating engaging means which allow the two parts to be brought together with relative axial movement in one rotational position of the parts, and which include camming and detent means which draw and lock the two parts together upon relative rotation of one of the parts to a second rotational position relative to the other.
Preferably, the camming and detent means include part-circular grooves in the first part, having undercut camming surfaces terminating in recesses, and retaining elements projecting from the second part, the retaining elements being movable through entranceways into the grooves with relative axial movement of the parts in one relative rotational position, and being capable of movement along said grooves upon relative rotation of the parts, preferably through about 90xc2x0 and, in any event, less than 180xc2x0, to the second rotational position at which the elements are retained in the recesses, these recesses providing detent means. A resilient element may be provided between the two parts, with the detent means tending to prevent movement of the retaining elements until the resilient element is compressed. The groove and retaining element arrangement is contained within the same xe2x80x9cfootprintxe2x80x9d area normally required of an adapter of this general type, so does not require additional space.
The provision of detent means as described means that the parts are positively locked together and the second part does not move when connectors are screwed onto or unscrewed from this part, as might happen if the parts were connected by a simple screw.
Preferably, the alignment sleeve is retained the second part, and when this part is separated from the first part the internal ferrule is accessible for cleaning.
It is common for the ends of ferrules to be slanted, so that two mating ferrules must be rotationally aligned. In order to meet the alignment requirements, the retaining elements and entranceways are differentiated so that the two parts can be connected together only in one particular rotational position. The parts have conventional means to ensure that the ferrules of mating connectors are properly rotationally aligned relative to the inner and outer parts.
In order to protect the ferrule of the first fiber against contamination, and also to protect a user""s eyes, the second part preferably has a cap connected thereto by hinge means which is biassed to close the cap over the ferrule of the internal fiber when no external connector is present. For this purpose, the second part has a partially flat side surface, and the cap is connected to the second part by a living hinge mounted on the flat side surface. The cap is recessed to fit over standard adapter receptacles capable of receiving FC, ST, SC, and preferably other types of connectors. The cap may be used on adapters which do not have the cooperating engaging means described above.
According to another aspect of the invention, there is provided an adapter for interconnecting optical fiber connectors, having a first part suitable for connection to a first optical fiber having an end ferrule, and having a second part suitable for receiving an optical fiber connector having a second optical fiber with an end ferrule, wherein said second part has a substantially flat side surface, and wherein a cap is connected to the second part by a living hinge having a flange mounted on said flat side surface, said cap having a hollow interior so as to be capable of closing over a projecting portion of the second part to prevent contamination of the internal optical fiber end ferrule.
When the adapter is mounted upon a panel, both of the first and second parts will normally be mounted on the same side of the panel. In the following specific description, the part that is closer to the panel will be termed the xe2x80x9cinnerxe2x80x9d part and the part further from the panel termed the xe2x80x9couterxe2x80x9d part. However, the invention is not restricted to adapters which are mounted on a panel or any other piece of equipment.